A laser machining apparatus in which a laser beam is focused by a focusing lens and performs the working operation while radiating the laser beam onto a workpiece is publicly known and is widely utilized. Further, a laser machining apparatus which works using both the laser beam and another auxiliary energy source such as a plasma jet or the like and thereby improving the working efficiency has been developed and is being used.
In the above-mentioned laser machining apparatus, although the working efficiency and working speed were remarkably improved as compared with conventional laser machining apparatus, the working efficiency and speed are still low and, particularly, in the case of cutting and working a thick workpiece or the like, it takes a long time and a high degree of working accuracy cannot be obtained.
Such a conventional laser machining apparatus using an auxiliary energy source performs the working by collecting the laser and the auxiliary energy onto the same irradiation point on a workpiece. When giving a relative movement between the workpiece and the irradiation point of the working laser beam and thereby performing the cutting work or welding work, etc., there is the problem that the heating by the auxiliary energy is not effectively utilized to the best advantage for the working by the laser beam.
In addition, in the case of working by collecting the working laser beam and the auxiliary energy onto the same irradiation point on a workpiece, the lens system for focusing the laser beam and the means for generating the auxiliary energy overlap at a certain portion, such that the arrangement of the apparatus becomes complicated and also its operation becomes troublesome.
On the other hand, although the auxiliary energy is provided to mainly heat a workpiece to a constant temperature and thereby to assist the working by the laser beam, since a portion of constant extent is heated by the irradiation of the auxiliary energy, in the case where the workpiece is relatively moving for the irradiation point of the working laser beam, a rear portion in the progressing direction of the working where the auxiliary energy is irradiated reaches a higher temperature than the front portion thereof. This is inconvenient since it results in wasted consumption of energy and causes distortion.